The present invention relates generally to a hologram-replicating (or copying) method and a volume hologram, and more particularly to a method for replicating (or copying) a volume hologram having an image of a scattering object recorded therein by a hologram replicating technique, wherein the diffraction of unnecessary light (zero-order light) is limited and a visual range (angle-of-view range) where the recorded image can be viewed is limited to a desired range, so that an image brighter than that in the original hologram plate can be displayed, and a volume hologram.
So far, it has been well known in the art that scattering light coming from a scattering object and reference light interfere in a volume hologram photographic material to record a volume hologram reconstructible in white illumination light. Also well known in the art is a hologram replicating technique wherein a reflection or transmission type volume hologram is provided thereon with another volume hologram photographic material, and laser light is allowed to be incident on said another photographic material or the original hologram plate so that said incident light and light diffracted by the volume hologram can interfere in said another photographic material, whereby the original volume hologram can be copied to obtain the same hologram.
When copying a volume hologram with a scattering object recorded therein by the hologram replicating technique, however, the angle of incidence of the copying laser light has been selected from those in the vicinity of the angle of incidence of the reference light used for recording the original hologram plate or otherwise no special care has been taken thereof at all. For this reason some problems have arisen. For instance, unnecessary interference fringes coming from light (zero-order light) produced by the regular reflection of light from the scattering object remain recorded in the copied hologram, or unnecessary diffracted light arises from unnecessary interference fringes because the visual range where the recorded image can be viewed is as wide as that of the original hologram plate. Consequently, no satisfactorily bright display can be obtained.